Fixes several compile issues I am seeing for my version of Visual Studio
related to an ambiguous call to `fpclassify`, which is called by `isnan`
and other similar functions, specifically for the `cl_half` type:
```
19>C:\Program Files (x86)\Windows Kits\10\Include\10.0.19041.0\ucrt\corecrt_math.h(401,1): error C2668: 'fpclassify': ambiguous call to overloaded function
19>C:\Program Files (x86)\Windows Kits\10\Include\10.0.19041.0\ucrt\corecrt_math.h(298,31): message : could be 'int fpclassify(long double) throw()'
19>C:\Program Files (x86)\Windows Kits\10\Include\10.0.19041.0\ucrt\corecrt_math.h(293,31): message : or 'int fpclassify(double) throw()'
19>C:\Program Files (x86)\Windows Kits\10\Include\10.0.19041.0\ucrt\corecrt_math.h(288,31): message : or 'int fpclassify(float) throw()'
19>C:\Program Files (x86)\Windows Kits\10\Include\10.0.19041.0\ucrt\corecrt_math.h(401,1): message : while trying to match the argument list '(_Ty)'
```
Some of these issues seem like differences in compiler behavior, but at
least one appears to have identified a legitimate bug.
Specifically, this change:
* Removes the special-case checks for finite half numbers for commonfns,
since this is already handled by `UlpFn`. (test with: `test_commonfns
degrees radians`)
* Assigns to temporary variables to eliminate the ambiguous function
call for relationals. (test with: `test_relationals relational*`)
* Properly converts from half to float when checking for NaNs for
select. This is the one that seems like a legitimate bug. (test with:
`test_select select_half_ushort select_half_short`)
* Uses `std::enable_if` to disambiguate a function call for spirv_new.
(test with: `test_spirv_new decorate_saturated*`)
If it's helpful, my specific Visual Studio version is:
```
Microsoft Visual Studio Professional 2019
Version 16.11.20
VisualStudio.16.Release/16.11.20+32929.386
```
I also have the Windows Software Development Kit 10.0.19041.685
installed.
* Added cl_khr_fp16 extension support for commonfns test (issue #142, commonfns)
* Added missing header due to presubmit check
* Corrected radians/degrees ulp calculations + cosmetic fixes
* Corrected presubmit code format
* Corrections related to code review
* Moved string format helper to test_common in separate header
* Added clang format for last commit
* Corrections related to code review
* Modified mix verification procedure for half type to only report max error
* Removed redundant condition for logging mix verification
* Corrected generator limits for half tests
* Unified common functions tests due to preparation for adding cl_khr_fp16 support
* Renamed base structure, few cosmetic corrections
* Added corrections due to code review
* Removed comment separators
* Added review related corrections
